It is well known that we are at a point of “Peak Oil” where discovery of new sources of oil is less than the amounts being depleted. There is also growing concern over pollution produced from burning fossil fuels, especially coal to generate electricity. Concurrently, demand for electricity continues to grow across the globe. Consequently, increasing effort is being devoted to developing devices that harness renewable energy sources to generate electricity. Wind turbines are one of these.
Turbines that operate in windy environments have traditionally fallen into descriptive categories defined by their axis of revolution relative to the wind and/or the ground. Vertical axis wind turbines (VAWTs) have blades that are generally parallel to their axis of spin and perpendicular to the ground while horizontal axis wind turbines (HAWTs) have blades that are generally perpendicular to their axis of spin and parallel to the ground. The VAWT and HAWT nomenclature popularly relates to the ground plane but is not dependent upon it.
In order to successfully generate usable energy, a wind turbine must minimize mechanical energy losses while producing the maximum practical extraction of torque from the wind. Wind turbines, though they need to be strong, should be as light as possible in order to minimize energy losses due to inertia and mechanical friction. Also, since the velocity and direction of the wind varies continuously, there is a need for turbines that can harness a wide range of wind velocities and often varying wind directions with the least internal mechanical energy loss. Because wind velocity varies greatly over the course of a year, it is important that wind turbines be able to harness both low and high velocity winds. Since it is often difficult to initiate movement of such devices, there is a particular need for wind turbines that are self-starting at lower wind speeds, just as there is a need for designs that produce structural and material efficiencies that handle the stresses experienced by wind turbines when operating at higher wind speeds.
Wind turbine devices, though producers of “green” energy, also must overcome their own environmental challenges. Increasingly people are objecting to the flickering shadows and noise generation of currently produced and installed HAWT wind turbines when they are within sight and earshot of homes, businesses, places of recreation, etc. HAWT turbines also tend to create problems for birds and bats as they can be struck by the wind turbine blades, or sustain internal organ damage due to the low pressures generated near the moving blades. Therefore, there is a need for new types of installed wind turbines that are aesthetically pleasing in appearance, fit more comfortably into their environment, and do not generate low pressures in the vicinity of their moving blades.
Finally, the art has not thus far provided efficient and practical large and medium scale wind turbines that can be placed and effectively used in congested and populated locations including in urban areas filled with buildings, including skyscrapers. Further, the wind turbine industry has not developed sufficiently efficient and otherwise acceptable turbines that can be successfully erected and operated in urban areas or atop tall buildings including skyscrapers to generate significant kilowatt output. The industry also has not recognized the potential of unique air flow accessible in such environments or how to best harness them efficiently. Therefore, the increased wind power available at the heights of tall buildings and the beneficial wind flow available across the tops of such buildings have not yet been efficiently harvested.
Finally, the wind turbine industry is increasingly plagued more by the infrastructure related costs of erecting ever taller turbines and getting the electricity that they produce to market rather than by the costs of the turbines themselves. These infrastructure utilization costs include the costs of erecting free-standing towers and the costs of new or upgraded electrical distribution grids that link the wind turbines and the electricity they produce to where it is used. Distance also can create considerable transmission line losses which may be as high as 20%. Such transmission line losses could be virtually eliminated by reducing transmission distance, if acceptably designed and efficient mid- to large-size turbines were available for placement in the urban environment, particularly on the top of tall buildings. Green, renewably generated electricity is easily used within these turbine-topped buildings by tenants and building management. Placement atop tall buildings would also eliminate the costs of erecting towers to support and elevate wind turbines.
The various embodiments of the present invention overcome these difficulties and meet operational requirements and more with devices that (a) are extremely lightweight and subject to very low friction and inertial losses; (b) can accommodate a wide range of wind velocities and varying wind direction; (c) allow feathering of the wind-receiving blades of the device to maximize power output and reduce drag in the reverse wind portions of the turbines' rotation; (d) maximize the torque (power) produced through just-in-time sensing of wind conditions at the blades which enhance feathering control and optimally maximize torque extraction; (e) have a visually appropriate appearance and do not generate low pressures in the vicinity of their moving blades; (f) are generally quiet in operation; (g) start up without external assistance in low winds; (h) can harness both high and low velocity winds (and address occasionally very high winds without structural failure; (i) are designed to resist centrifugal forces on turbine components; (j) can be placed atop tall buildings where the wind benefits of height and other specific conditions can be captured; (k) capture unique air flow from building-induced updraft available at skyscrapers; and (l) may be used to supply power directly via a minimal transmission distance to the very buildings onto which they are erected thereby minimizing power transmission losses of that electricity that is generated by the turbine.